Signaling in Plants: Study with Video Lessons, Practice Problems & Examples

Plant signaling differs significantly from animal signaling, primarily through the use of serine-threonine kinases instead of tyrosine kinases. Key signaling molecules in plants include auxins, which promote growth, and ethylene, which triggers fruit ripening. Other important processes involve stem elongation and light sensing. Unlike animals, plants lack certain signaling pathways such as JAK-STAT and Notch. Understanding these unique signaling mechanisms is crucial for advanced studies in plant biology.

Plant Signaling

Hi. In this video, we're going to be talking about signaling in plants. So signaling evolved differently in plants and animals. And that's the reason why it has a separate video. And so, a lot of the things that we've talked about in animals don't necessarily have similar things in plants or act in a similar way. So for instance, plants have receptor kinases like humans and mammals and other animals, but their largest class isn't Tyrosine Kinases, which is what I've said before, but instead Serine Threonine Kinases. Additionally, plants don't have homologs or similar molecules for things like JAK, STAT, which we talked about, but also for ones that we didn't talk about, but are also still really important signaling pathways, things like Notch, Wnt, and Hedgehog. Now, we didn't talk about these because you don't need to know the mechanisms yet. If you take more advanced biology classes, you will need to know these mechanisms, but plants don't have them, and so, that's super important. Now instead, plants have a lot of signaling molecules that animals don't have. So, I bolded and highlighted now the two that you're going to need to know, and then italicized the ones that are also different, but also aren't as important and you're less likely to be questioned on them. So the first there are auxins, which stimulate plant growth. And then you have ethylene, which stimulates fruit ripening. So these are the two main ones you are going to want to know. But there is all these other ones as well that, you know, have to do with stem elongation, cell division, cell dormancy, sensing light, you can imagine is super important for plants. So all these signaling molecules are different in plants and very specific for plants, but not animals. So, it's all very different in plants. So, with that, let's now move on.

Plant and Animal signaling evolved differently.

• A. True
• B. False

Which signaling molecule stimulates fruit ripening?

• A. Auxins
• B. Ethylene
• C. Phytochromes
• D. Gibberelins

Here’s what students ask on this topic:

What are the main differences between plant and animal signaling pathways?

Plant signaling pathways differ significantly from animal signaling pathways. In plants, the primary class of receptor kinases is serine-threonine kinases, whereas in animals, it is tyrosine kinases. Additionally, plants lack homologs for several key animal signaling pathways, such as JAK-STAT, Notch, Wnt, and Hedgehog. Instead, plants have unique signaling molecules like auxins, which promote growth, and ethylene, which triggers fruit ripening. Other plant-specific signaling molecules are involved in processes like stem elongation, cell division, cell dormancy, and light sensing. Understanding these differences is crucial for advanced studies in plant biology.

What role do auxins play in plant signaling?

Auxins are a crucial class of signaling molecules in plants that primarily stimulate plant growth. They regulate various aspects of plant development, including cell elongation, root formation, and differentiation. Auxins are also involved in phototropism (growth towards light) and gravitropism (growth in response to gravity). By influencing the expression of specific genes, auxins help coordinate the plant's growth and response to environmental stimuli. Understanding auxin signaling is essential for comprehending how plants adapt and thrive in their environments.

How does ethylene affect plant processes?

Ethylene is a plant hormone that plays a significant role in various plant processes, most notably fruit ripening. It acts as a signaling molecule that triggers the ripening process, leading to changes in color, texture, and flavor of the fruit. Ethylene also influences other aspects of plant development, such as leaf abscission (shedding of leaves), flower wilting, and response to stress conditions. By understanding ethylene signaling, researchers can better manage agricultural practices, such as controlling the timing of fruit ripening and extending the shelf life of produce.

Why don't plants have JAK-STAT, Notch, Wnt, and Hedgehog signaling pathways?

Plants do not have JAK-STAT, Notch, Wnt, and Hedgehog signaling pathways because these pathways are specific to animal systems and have evolved to meet the unique physiological and developmental needs of animals. Instead, plants have developed their own distinct signaling mechanisms that are better suited to their stationary lifestyle and environmental interactions. For example, plants rely on serine-threonine kinases and unique signaling molecules like auxins and ethylene to regulate growth, development, and responses to environmental stimuli. These plant-specific pathways are crucial for processes such as phototropism, gravitropism, and stress responses.

What are some other important signaling molecules in plants besides auxins and ethylene?

Besides auxins and ethylene, plants have several other important signaling molecules that regulate various physiological processes. These include cytokinins, which promote cell division and shoot formation; gibberellins, which are involved in stem elongation and seed germination; abscisic acid (ABA), which regulates stress responses and seed dormancy; and brassinosteroids, which are essential for cell expansion and differentiation. Additionally, plants use light-sensing molecules like phytochromes and cryptochromes to regulate growth and development in response to light conditions. Understanding these signaling molecules is vital for comprehending the complex regulatory networks in plants.